Combustion engines using various fuels, and notably diesel fuel, often utilize a common rail fuel system, where pressurized liquid fuel is delivered to a common rail that supplies the fuel to a plurality of fuel injectors. Common rail fuel systems may be relatively sensitive to particulate contamination. Even fine particles present in high-pressure fuel pumps, injectors, and other components can damage the system or diminish system performance. Particulates can be present in a fuel system for a variety of reasons, including contamination in the fuel itself or debris dislodged from engine components due to wear or as a result of various other physical and/or chemical processes. Servicing also provides various opportunities for contaminants to be introduced into the system. For example, if the fuel system undergoes maintenance, often fuel must be drained and components must be inspected, cleaned, and/or replaced. Unfiltered fuel may have a variety of contaminants such as wax, asphaltines, rust or dirt. High pressure fuel systems may be especially sensitive to contaminants due to tight clearances, high pressures, and the rapid speed of moving parts. If contaminants are not removed before entering a high pressure side of the fuel system, they may cause rapid wear and failure of fuel system components such as the fuel injector plungers and barrel as well as control valves. Minimum clearances in fuel injectors may be less than 2.5 microns in some instances, meaning microscopic particles can cause scratching and scuffing and potentially valve seizure. Further, contaminants may erode the mating parts of control valves, resulting in poor sealing. To address these and other concerns, fuel filters are positioned at various locations within the system and swapped out for fresh filters at periodic service intervals. Such routine maintenance as well as repairs may require that fuel be drained from the system, and then the drained fuel replaced and the system brought back up to pressure before the engine can be operated.
In a practical setting, reducing the time it takes to prime the fuel system may be seen as advantageous, especially for professionals as fuel system priming is a passive process that may require little to no action on the part of mechanics, vehicle owners, or other parties undertaking the maintenance or repair efforts. Rather than sitting idly by, persons working on fuel systems may attempt to hasten the priming process. One common technique for reducing the time it takes to prime the system is to fill the new filter with fuel, therefore diminishing the need for the system to be supplied with additional fuel and hastening the speed with which the fuel system can be made ready for service for various reasons. Pre-filling a new filter with fuel, however, can introduce unfiltered fuel to a “clean side” of the fuel system and cause particulates to be introduced into the system, thereby increasing the possibility of damaging or diminishing performance. U.S. Pat. No. 9,316,187 to Saler et al. sets forth a system for priming a diesel fuel engine in which a fuel monitoring mechanism may be used to detect the presence of fuel at a fuel filter. While this and other solutions may allow for fuel detection, no mechanism for detecting, calculating, or otherwise sensing activities that likely introduce unfiltered fuel appears known.